1. Field of the Invention
This invention relates to a method and apparatus for determining the condition of a gaseous mixture and, in particular for determining the moisture content, the molecular oxygen content and/or the content of other constituent gases in a gaseous mixture containing oxygen. Specifically, this invention relates to the use of a heated, ceramic, electrochemical cell for making these determinations.
2. Description of the Prior Art
Prior to this invention, a wide variety of devices and methods were employed for determining or measuring the amount of water vapor in a gaseous atmosphere. Some of the methods or devices used measured the equilibrium partial pressure of water in the gas. Others measured the temperature at which the condensation of water begins to occur upon cooling. Typical of the devices employed were those commonly identified as dew point hygrometers and absorption hygrometers. Characteristically, however, all such commonly employed devices were limited in their range of usefulness to relatively low concentrations of water, generally, under 20 percent by volume.
The use of a heated, ceramic, electrochemical cell is per se known in the art of gas analysis. Such cells are known to be useful to detect oxygen and/or combustibles in combustible mixtures and in the combustion by-products of a combustion process. Typical examples of these cells are disclosed in U.S. Pat. Nos. 3,597,345, 3,616,408, 3,865,707 and 3,869,370, the disclosures of which are incorporated herein by reference. However, as far as it is known, these cells have never been used to determine moisture content or the content of other gases in a gaseous mixture in accordance with the principles of this invention.
Accordingly, it has been found that a need exists for an improved method and apparatus for determining the moisture content of a gaseous mixture containing oxygen, as well as for determining the content of other gases in such a gaseous mixture. Moreover, it is found desirable, in conjunction with such an improved method and apparatus, to provide the capability of being able to determine the free or molecular oxygen content of said gaseous mixture. In particular, a need exists to be able to rapidly and reliably measure gaseous constituents in gas mixtures containing oxygen, to be able to measure the moisture content of such a gas to a much higher concentration than was heretofore readily accomplished and to be able to perform these determinations on such gaseous mixtures at highly elevated temperatures and/or on such gaseous mixtures containing corrosive gases, such as acid gases.